An exciting day for cosmologists

Why the hoopla among astronomers today? It’s because scientists collecting data from the Wilkinson Microwave Anisotropy Probe, or the WMAP satellite, have released their second batch of results.

Although not as earth-shattering as the first batch, which revealed the age of the universe to be about 13 billion years with spectacular precision, the new results provide lots of great information.

The New York Times has a really nice article on the results here. But I actually prefer Phil Plait’s exuberant summary at Bad Astronomy, where he explains that we’ve now been able to glimpse back into the first trillionth of a second of the universe’s expansion. It’s a validation of the Big Bang Theory:

The big result is that the light left over from this early time matches the models of the Big Bang and Inflation very well. The Big Bang model says the Universe started in a single moment, and has been expanding since then.

Inflation is this weird idea that for a teeny tiny fraction of a second, the Universal expansion accelerated hugely. Inflation explains a lot of problems that had cropped up in the Big Bang model as observations got better.

What’s nice about inflation is that it explains a wide variety of issues including problems in particle physics as well as cosmology without really changing what happened in the very early Universe, before inflation. In other words, the Big Bang and inflation are separate models which fit together to explain what we see in the sky.

We’ve also learned that the first stars formed about 400 million years after the universe first burst onto the scene. Someday, hopefully within my lifetime, we’ll have telescopes to see that far away, powerful enough to see the first stars of the universe.

So what does the WMAP probe measure? It measures something called the cosmic microwave background radiation, which is a fancy way of saying it’s the energy left behind after the Big Bang. The detritus of the initial explosion, if you will.

By studying the density and distribution of this energy across the sky, modern scientists, like forensics experts, can piece together what the initial explosion was like. That humanity can put these pieces together is something our species should celebrate.

BTW Eric, you never did answer my question that I proposed for the “stump the scholar” post a while back. I really do want to know why the Hydrogen band is the quietest, it makes no sense to me since Hydrogen is the most abundant element in the universe.

Many physicists that I know (myself included) believe that these CMB anisotropy experiments will be Nobel Prize material within a few years. Look for the prize to be shared among: the leader of the first CMB measurements by a satellite known as COBE (George Smoot, I think), the leader of the WMAP project (Charles Bennett), and the theorist who came up with the inflation model (Alan Guth). That’s my own personal prediction – you heard it here first. Another possibility is that it would be awarded to theorists only: Guth and Andrei Linde, for example. That would be a pity, IMHO, because the experiments are (a) unbelievably hard and (b) amazingly useful.An interesting side note: as an undergraduate, I had a class with Guth. A very funny guy, much more approachable than some other professors. Of course, he was much younger then…

That’s what I would call an unanswerable question. It is the realm of faith at this point, not experimental science.

The real question that bends my mind is this: What medium is our current universe expanding into? I.e., what is beyond our universe? Is it a void? If so, how big is the void? Are there walls somewhere? Does it extend into infinity? If not, what’s behind the walls?

I just finished reading The Cosmological Landscape by cosmologist Leonard Susskind, now at Stanford. It’s kind of a “Cosmology for Dummies” primer but interesting. Two things stand out that fit these latest discoveries.

His purpose of the book was to address the Anthropic Principle, which says that because there are intelligent beings capable of observing the universe, the universe must have been designed for that purpose by some intelligent entity. Susskind’s premise is that the AP has nothing to do with religion but with the simple observation that this universe (he’s a major proponent of the “multiverse” or “megaverse” concept composed of billions of “pocket universes,” among which is ours) is a combination of numerous “lucky circumstances” that make it perfect for our form of life. Not intelligent design but the result of huge-numbers probabilities.

The other idea he proposes is that due to Inflation (a concept he enthusiastically endorses) scientists will soon discover that the way to continue examining how the universe began will be to stop looking inward (microscopically/sub-microscopically) and look outward. When the Big Bang occurred, this “bubble” exploded and inflated at a tremendous rate (confirmed by these recent discoveries), and is still inflating infinitely. Therefore, the subatomic particles are also inflating, which means that the earliest particles may now be spread out in immense “tangled strings” (Susskind is one of the originators of String Theory), which can be observed and interpreted if we can figure out the algorithms to discern the pattern.

Which means that the WMAP project will likely discover this pattern sometime in the (near?) future. An exciting possibility.

There is something like an answer to the question “what was before the big bang?” although I will warn you that the answer is not much more satisfying than Eric’s response. The answer is: the question doesn’t make sense because there was no “before”. Remember that Einstein taught us that space and time are not two distinct things, but in fact are two different ways to look at the same thing. There is no ‘space’ and ‘time’, only ‘spacetime’. Which means, “before the big bang” is a phrase that doesn’t mean anything, because, since the three dimensions of space didn’t exist, neither did time. There simply was no ‘before’. Time didn’t exist. A mind-bending concept, to be sure, but if modern physics teaches us anything, it is that the true nature of the universe is pretty mind-bending. In this case, what it teaches us is that the description: “there was something floating around and then it exploded” is simply wrong.

The question Eric poses, “what is the universe expanding into?” is somewhat more subtle, believe it or not. And has an equally unsatisfying answer. First of all, there is the concept of the ‘observable universe’, which is the universe that we can see. The parts that are within 13.7 billion light years (give or take). Anything further away than that is unobservable, because signals from there simply can’t ever reach here. But we still can ponder the expansion of the observable universe, and in that case the question has a similar answer to the time question: it isn’t expanding into anything, because the thing it would be expanding into would also be part of the universe, of course. One can think about this question using an analogy, which (like all analogies) can only be taken so far. Consider a bunch of raisins embedded in a big lump of dough. When we bake the whole thing, the dough rises, the whole lump expands, and if you are one of the raisins then it looks to you as if all the other raisins are moving away from you in all directions. This analogy is good because it allows you to picture how everything can be moving away from everything else due to expansion. But it is bad because raisin bread DOES expand into empty space, whereas the expansion of spacetime is essentially due to the creation of new spacetime rather than the expansion of some finite-sized thing into a larger volume.Mind-bending. But fun.

Interesting comments. Quantum mechanics on the very smallest scales and cosmology on the very largest scales are, no doubt, weird birds beyond the understanding of most of us. I mean, who among us can wrap their brains around multi-dimensional string theory?

Perhaps that’s why I have such great admiration for the particle physicists and cosmologists who are probing these great frontiers at the very small and the very large. There’s far too much mathematics in these places for my tastes and abilities. I realized that after squeaking through four semesters of calculus and vowing never to return to such horrors.

As for the Nobel Prizes you mentioned earlier, I have to agree that Guth is almost certainly to be named. But the big question is whether the COBE folks or Bennett will accompany him, or the theorists who came after Guth, such as Andrei Linde, Andreas Albrecht and Paul Steinhardt. But what, also, of the work by David Wilkinson and Francesco Melchiorri? You get three slots.

Inflation is very compelling, but very far from having been proven. For this reason, I can not see a Nobel being handed to Guth (or linde or steinhardt) as the situation stands now. I mean, there is a consensus that the universe experienced a brief period of insane expansion, but far from consensus what the mechanism is or how to prove the mechanism.

That said, the results from WMAP are most certainly worth nobel prizes, but I’m not quite sure which particular people deserve them.